Collapsible knob assembly and retaining spring therefor

Abstract

A D-shaped retaining spring couples a knob to a shaft. The spring has a flange abutting the end face of the knob to fix the spring position in a cavity of the knob. Alternatively, instead of the flange, the inner end of the spring abuts a shoulder in the cavity to fix the spring position. In either case, the inner end of the spring has a tab extending radially inward at a location spaced from the cavity end wall to define a stop for the end of the shaft thereby holding the knob where it can protrude from an instrument panel for normal operation. An axial impact force on the knob causes the tab to yield, allowing the knob to slide further onto the shaft and into the panel for the purpose of avoiding injury due to striking the knob during a crash.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. A collapsible knob assembly comprising: a rotatable shaft for actuating a control device;   a knob on the shaft having a cavity for receiving an end of the shaft, the cavity having an inner end wall;   a retention spring within the cavity and surrounding the shaft for frictionally securing the knob to the shaft;   first stop means on the spring for engaging the shaft and for holding the shaft end spaced from the end wall of the cavity; and   second stop means for holding the spring fixed in the cavity;   one of the stop means comprising means for deforming under stress to allow collapse of the assembly upon axial impact on the knob including yieldable element on the spring, thereby moving the end wall of the cavity toward the shaft end upon impact.   
     
     
       2. The invention as defined in claim 1 wherein the first stop means comprises a yieldable tab on the spring spaced from the end wall of the cavity for holding the shaft end spaced from the end wall. 
     
     
       3. The invention as defined in claim 1 wherein the second stop means comprises a portion of the spring which abuts the knob to fix the spring position in the knob cavity. 
     
     
       4. The invention as defined in claim 1 wherein: the spring includes a body portion contained within the cavity of the knob; and   the second stop means comprises a flange which extends radially outwardly from the body to abut a surface of the knob.   
     
     
       5. The invention as defined in claim 1 wherein: the spring includes a body portion contained within the cavity of the knob and having an inner end spaced from the end wall of the cavity and an outer end adjacent an outer surface of the knob;   the first stop means comprises a tab on the inner end extending inward to abut the shaft end;   the second stop means comprises a flange which extends radially outwardly from the outer end of the body to abut the outer surface of the knob.   
     
     
       6. The invention as defined in claim 5 wherein the body is D-shaped to define a flat side; the first stop means comprises an L-shaped tab extending from the flat side and defining a bend having a radius, the radius being selected to establish a desired yield force; and   the tab further having a portion extending radially inward from the bend.   
     
     
       7. The invention as defined in claim 1 wherein: the spring includes a body portion contained within the cavity of the knob; and   the second stop means comprises a shoulder in the cavity spaced from the end wall, which shoulder abuts the spring.   
     
     
       8. The invention as defined in claim 1 wherein: the spring includes a body portion contained within the cavity of the knob and having an inner end spaced from the end wall of the cavity and an outer end adjacent an outer surface of the knob;   the first stop means comprises a tab on the inner end extending inward to abut the shaft end;   the cavity comprises a stepped bore which defines a shoulder for engaging the inner end of the spring thereby comprising the second stop means.   
     
     
       9. The invention as defined in claim 8 wherein the stepped bore has a first portion adjacent the end wall with a diameter sufficient to accept the shaft and a second portion with a diameter sufficient to accept the spring. 
     
     
       10. A retention spring for yieldably fixing a shaft in a cavity of a knob comprising: a sheet metal spring having a body for surrounding and frictionally gripping the shaft;   the spring having first and second stop means integral with the body;   the first stop means comprising an abutment for limiting insertion of the shaft into the knob cavity;   the second stop means comprising a spring portion for engaging the knob to fix the spring position in the cavity; and   means comprising one of the stop means for yielding upon application of an axial force to effect full insertion of the shaft into the cavity.   
     
     
       11. The invention as defined in claim 10 wherein the means comprising one of the stop means is L-shaped and comprises an axial portion extending from the spring body and a radial portion joined by a radius to the axial portion, wherein the radius affects the impact force required to cause the means comprising one of the stop means to yield. 
     
     
       12. The invention as defined in claim 10 wherein: the body is D-shaped to define a flat side;   the first stop means comprises an L-shaped tab extending from the flat side and defining a bend having a radius, the radius being selected to establish a desired yield force; and   the tab further having a portion extending radially inward from the bend.   
     
     
       13. The invention as defined in claim 10 wherein the first stop means comprises a yieldable tab on a first end of the spring body extending inward for engaging the shaft and subject to deformation upon application of an axial impact force to allow full insertion of the shaft into the cavity. 
     
     
       14. The invention as defined in claim 10 wherein the second stop means comprises an inner end of the spring body which is adapted to engage a feature of the knob. 
     
     
       15. The invention as defined in claim 10 wherein the second stop means comprises a flange extending outward from an outer end of the spring body to engage a surface of the knob.